The present invention relates to a spindle for fastening a plurality of rotor elements of a gas turbine engine together as well as a method for assembling the rotor elements utilizing the fastening spindle.
A gas turbine engine, such as an aircraft turbojet engine, typically has several stages or rotary elements comprising rotor wheels or discs with turbine blades attached thereto. The rotary elements are usually interconnected by bolts extending generally parallel to the rotational axis of the elements and extending through radial flanges formed on each of the rotary elements. This has proven a satisfactory method of fastening the rotary elements together where there is sufficient access on either side of the parts to install the bolt or threaded stud and attach nuts thereto. Generally, the bolts are placed through the flanges from the upstream to the downstream sides and are locked into position by holding the upstream head or nut while tightening a fastening nut on the downstream end. Devices of this type are shown in British Pat. No. 2,057,617 and French Pat. No. 2,065,837. However, these devices cannot be used when the rotor element flanges are located close to the rotor disc where the space between the disc and the flange is too small to place the bolt or stud into the hole in the flange.
To alleviate this problem, it has been proposed to utilize a threaded spindle having a central flange which is placed between the rotor elements such that the threaded spindle extends through holes formed in both of the rotor elements. This structure is shown in U.S. Pat. No. 3,447,822 and French Pat. No. 1,056,070. These devices have not completely solved the problem since they do not allow sufficient control over the tightening of the nuts on the threaded spindle. Furthermore, there are instances after the rotor elements are stacked together in which it is not possible to reach the upstream nut attached to the spindle thereby preventing the downstream nuts from being adequately tightened. Thus, utilizing this sytem, it is not possible to adequately verify if the nuts are properly tightened against the flange inside the upstream cavity. Furthermore, when the downstream nuts are being tightened, the spindles have a tendency to rotate, thereby loosening the upstream nuts.
The only way to verify the tightening of the upstream and downstream nuts is to measure the length of the spindle projecting outside the downstream nut. This has proven unsatisfactory since, if the tightening is improper, it is necessary to completely remove the threaded spindle and start the fastening process all over again.